This invention relates in general to preventing the production of particulate materials through a wellbore traversing an unconsolidated or loosely consolidated subterranean formation and, in particular to, an apparatus and method for obtaining a substantially complete gravel pack within an interval of the wellbore.
Without limiting the scope of the present invention, its background is described with reference to the production of hydrocarbons through a wellbore traversing an unconsolidated or loosely consolidated formation, as an example.
It is well known in the subterranean well drilling and completion art that particulate materials such as sand may be produced during the production of hydrocarbons from a well traversing an unconsolidated or loosely consolidated subterranean formation. Numerous problems may occur as a result of the production of such particulates. For example, the particulates cause abrasive wear to components within the well, such as tubing, pumps and valves. In addition, the particulates may partially or fully clog the well creating the need for an expensive workover. Also, if the particulate matter is produced to the surface, it must be removed from the hydrocarbon fluids by processing equipment at the surface.
One method for preventing the production of such particulate material to the surface is gravel packing the well adjacent the unconsolidated or loosely consolidated production interval. In a typical gravel pack completion, a sand control screen is lowered into the wellbore on a workstring to a position proximate the desired production interval. A fluid slurry including a liquid carrier and a particulate material known as gravel is then pumped down the workstring and into the well annulus formed between the sand control screen and the perforated well casing or open hole production zone.
The liquid carrier either flows into the formation or returns to the surface by flowing through the sand control screen or both. In either case, the gravel is deposited around the sand control screen to form a gravel pack, which is highly permeable to the flow of hydrocarbon fluids but blocks the flow of the particulates carried in the hydrocarbon fluids. As such, gravel packs can successfully prevent the problems associated with the production of particulate materials from the formation.
It has been found, however, that a complete gravel pack of the desired production interval is difficult to achieve particularly in long or inclined/horizontal production intervals. These incomplete packs are commonly a result of the liquid carrier entering a permeable portion of the production interval causing the gravel to form a sand bridge in the annulus. Thereafter, the sand bridge prevents the slurry from flowing to the remainder of the annulus which, in turn, prevents the placement of sufficient gravel in the remainder of the annulus.
Prior art devices and methods have been developed which attempt to overcome this sand bridge problem. For example, attempts have been made to use devices having perforated shunt tubes or bypass conduits that extend along the length of the sand control screen to provide an alternate path for the fluid slurry around the sand bridge. It has been found, however, that shunt tubes installed on the exterior of sand control screens are susceptible to damage during installation. In addition, it has been found, that it is difficult and time consuming to make all of the necessary fluid connections between the numerous joints of shunt tubes required for typical production intervals.
Therefore a need has arisen for an apparatus and method for gravel packing a production interval traversed by a wellbore that overcomes the problems created by sand bridges. A need has also arisen for such an apparatus that is not susceptible to damage during installation. Further, a need has arisen for such an apparatus that is not difficult or time consuming to assemble.
The present invention disclosed herein comprises an apparatus and method for gravel packing a production interval of a wellbore that traverses an unconsolidated or loosely consolidated formation that overcomes the problems created by the development of a sand bridge between a sand control screen and the wellbore. Importantly, the apparatus of the present invention is not susceptible to damage during installation and is not difficult or time consuming to assemble.
The apparatus for gravel packing an interval of a wellbore of the present invention comprises an outer tubular forming a first annulus with the wellbore and an inner tubular disposed within the outer tubular forming a second annulus therebetween. Typically, the inner tubular is positioned around a sand control screen. Together, the sand control screen and the apparatus of the present invention are assembled at the surface and run downhole to a location proximate the production interval. A portion of the side wall of the outer tubular is an axially extending production section that includes a plurality of openings. Another portion of the side wall of the outer tubular is an axially extending nonproduction section that includes one or more outlets. Similarly, a portion of the side wall of the inner tubular is an axially extending production section that is substantially circumferentially aligned with the production section of the outer tubular. Another portion of the side wall of the inner tubular is an axially extending nonproduction section that is substantially radially aligned with the nonproduction section of the outer tubular. The production section of the inner tubular has a plurality of openings therethrough, but the nonproduction section of the inner tubular has no openings therethrough.
The volume within the second annulus between the nonproduction sections of the outer and inner tubulars is an axially extending slurry passageway. The volume within the second-annulus between the production sections of the outer and inner tubulars is an axially extending production pathway. An isolation member, which is disposed within the second annulus, defines the circumferential boundaries of the production pathway and the slurry passageway and prevents fluid communication between the production pathway and the slurry passageway. The isolation member also defines the axial boundaries of the production pathway. As such, when a fluid slurry containing gravel is injected through the slurry passageway, the fluid slurry exits the slurry passageway through the outlet leaving a first portion of the gravel in the first annulus. Thereafter, the fluid slurry enters the openings in the outer tubular leaving a second portion of the gravel in the production pathway. Thus, when formation fluids are produced, the formation fluids travel radially through the production pathway by entering the production pathway through the openings in the outer tubular and exiting the production pathway through the openings in the inner tubular. The formation fluids pass through the first portion of the gravel in the first annulus prior to entry into the production pathway and the second portion of the gravel in the production pathway which filters out any particulate materials in the formation fluids. Formation fluids are prevented, however, from traveling radially through the slurry passageway as there are no openings in the nonproduction section of the inner tubular.
More specifically, the isolation member disposed within the second annulus may have a pair of substantially parallel, circumferentially spaced apart, axially extending members that radially extend between the outer and inner tubulars and a pair of substantially parallel, axially spaced apart, circumferentially extending members that radially extend between the outer and inner tubulars that define the production pathway and the slurry passageway and prevent fluid communication therebetween.
In one embodiment of the present invention, an actuatable device may be disposed within each of the outlets to selectively allow and prevent the fluid slurry from flowing therethrough. The actuatable devices may, for example, be pressure actuated devices, electrically actuated devices, acoustically actuated devices or the like. Suitable actuatable devices may include rupture disks or valves, such as one way valves.
Alternatively, the outlets may each have an exit tube disposed therein. The exit tubes may, for example, be positioned partially within the second annulus, partially within the first annulus or both. As yet another alternative, an insert member may be disposed at least partially within each of the outlets to prevent erosion of the outlets.
In embodiments of the present invention that have more than one outlet, the outlets may have various sizes and shapes. In addition, certain embodiments of the present invention may include multiple production pathways and multiple slurry passageways. In such embodiments, the outlets of the various slurry passageways may be at different axial positions along the outer tubular.
Commonly, more than one such apparatus for gravel packing an interval of a wellbore must be coupled together to achieve a length sufficient to gravel pack an entire production interval. In such cases, multiple sections of the apparatus of the present invention are coupled together, for example, via a threaded connection. Also, in such cases, the slurry passageways of the various sections are in fluid communication with one another allowing an injected fluid slurry to flow from one such apparatus to the next, while the production pathways of the various sections are in fluid isolation from one another.
In a method for gravel packing an interval of a wellbore of the present invention, the method comprises providing a wellbore that traverses a formation, either open hole or cased, perforating the casing, in the cased hole embodiment, proximate the formation to form a plurality of perforations,
locating a sand control screen within the wellbore proximate the formation, positioning the gravel packing apparatus around the sand control screen to form a first annulus between the gravel packing apparatus and the wellbore, injecting a fluid slurry containing gravel through the slurry passageway such that the fluid slurry exits through the outlets into the first annulus, depositing a first portion of the gravel in the first annulus, depositing a second portion of the gravel in the production pathway by injecting a portion of the fluid slurry through openings in the outer tubular and terminating the injection when the first annulus and the production pathway are substantially completely packed with gravel. In addition to injecting the fluid slurry containing gravel through the slurry passageway, in some embodiments, the fluid slurry may also be injected down the first annulus.